The present invention relates to a method for removing wax from a pulp furnish and, more particularly, a method from removing wax from a pulp furnish containing waxed old corrugated containers.
Today many paper mills are utilizing recycled fiber as a portion of their papermaking furnish. Recycled fiber is a valuable raw material, though it is inherently weaker than virgin fiber and contains contaminants which effect system cleanliness and appearance. Many new chemistry technologies are emerging to improve the appearance and strength of recycled fiber containing furnishes, as well as improving system cleanliness. Raw materials of reduced cost and quality such as waxed old corrugated containers (wOCC), mixed office waste (MOW), and curbside mixed waste (CMW) may be utilized without loss in appearance and paper properties when chemical aids to pulp cleaning are incorporated. Replacement of 10% of the OCC with wax saturated OCC would represent a significant economic savings for the paper mill.
The present invention provides a method for removing wax from a pulp furnish. More specifically, a method for recycling waxed old corrugated containers (wOCC) is provided. In the method, waxed OCC is first separated into fibers and wax, and then the wax is separated from the fibers. The separation of wax from the fibers is effected through the utilization of agglomerization chemicals. The method of the invention provides fibers from waxed OCC that preferably include less than about 0.5% by weight wax.
Through the method of the invention, waxed OCC can be recycled and used in a conventional pulping operation. A pulper furnish containing 10% wax saturated boxes has 95% yield through the operation. The wax content of pulp produced by the method meets the levels commonly accepted by the papermaking industry.
In the method, agglomeration chemicals effectively increase the size of the wax particles removed from the fibers. The size increase facilitates their removal in the screening and cleaning stages in the mill. The chemicals that provide wax removal and agglomeration include sodium sulfate, potassium sulfate, d-limonene, sodium metasilicate, lauryl sulfate, propylene carbonate, and mixtures of these chemicals. In a preferred embodiment, the method further includes the addition of a caustic material such as sodium hydroxide at the pulping stage which enhances wax separation from the fiber.